KR20070115338A - Cogeneration system for a feul cell and method thereof - Google Patents

Abstract

A cogeneration system using fuel cells is provided to withdraw heat energy from waste heat generated from the generation system through a simplified route. A cogeneration system using fuel cells includes: a steam-generating unit(10) which withdraws reactants and waste heat discharged from a reformer(1) and a fuel cell stack(3) and generates steam using the reactants and waste heat; a generation unit(21,22) which generates electric energy using steam generated from the steam-generating unit; a condenser(30) which withdraws steam discharged from the generation unit and subjects the steam to low-pressure expansion; and a pressurization unit(50) which applies pressure to working fluid supplied from the condenser, and sends back the working fluid to the steam-generating unit.

Description

Cogeneration System and Cogeneration System Using Fuel Cells {Cogeneration system for a feul cell and Method}

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to

1 is a block diagram of a fuel cell power generation system according to a preferred embodiment of the present invention.

Figure 2 is a schematic diagram of a steam generating means according to a preferred embodiment of the present invention.

<Description of main reference numerals in the drawings>

1 ... reformer 3 ... fuel cell stack

5. Power transmission means 10 ... Steam generation means

17 Heating means 21 Turbines

22 ... generator 30 ... condenser

40.Heating / hot water supply device 50 ... Pressure means

The present invention relates to a cogeneration system and a cogeneration system using a fuel cell, and more particularly, to a cogeneration system and a cogeneration system capable of efficiently recovering and reusing heat energy generated from a fuel cell power generation system. .

A power generation system using a fuel cell decomposes air containing hydrogen and oxygen contained in a hydrocarbon-based material such as methanol, ethanol or natural gas through an electrochemical reaction, and directly converts electrons generated in the process into electrical energy. It is a power generation system that changes.

A power generation system using a fuel cell is basically a fuel tank for storing fuel, a fuel pump for transferring the fuel, a reformer for generating hydrogen gas, and a fuel cell stack (hereinafter, referred to as a stack) that generates electric energy by generating electrons. ).

The reformer receives fuel and water stored in the fuel tank through the operation of the fuel pump, and reforms the fuel and water by steam reforming, partial oxidation, autothermal reforming, and direct decomposition. The above fuel is converted into a hydrogen-rich reformed gas through a method such as direct cracking, plasma catalytic reforming, or sorption enhanced reaction process. In addition, the reformed gas generated in the reformer contains harmful substances such as carbon monoxide, and the reformer purifies the hazardous substances and supplies them to the stack.

On the other hand, the stack includes an anode electrode and a cathode electrode, the hydrogen gas supplied from the reformer is injected into the anode electrode, the oxygen supplied from the outside air is injected into the cathode electrode. Accordingly, an oxidation reaction of hydrogen gas occurs at the anode electrode, and a reduction reaction of oxygen occurs at the cathode electrode. As a result, water and electrons are generated in the stack due to oxidation and reduction reactions of gases, and electric energy is generated by the movement of the electrons. In addition, due to the oxidation and reduction reactions, a predetermined heat energy is generated in the stack, which is applied to the water produced by the chemical reaction.

In the power generation system using the fuel cell configured as described above, high heat energy is generated due to a chemical reaction in the reformer and the fuel cell stack. When the heat energy is mostly emitted to the outside, the conversion efficiency of the fuel (fuel is converted into electric energy) Efficiency) may be lowered. To prevent this, the power generation system using the fuel cell is provided with a plurality of heat exchangers for recovering the heat or waste heat.

However, when a plurality of heat exchangers are provided in a power generation system using a fuel cell, the system becomes complicated, and the length of the pipe is increased to cause an internal pipe loss (for example, a pressure drop).

In addition, a system designed to use waste heat generated in a power generation system using a fuel cell does not directly recover and use the working fluid itself, and recovers only the latent heat of the working fluid through a heat exchange means. have.

The present invention is to solve the above problems, to provide a cogeneration system and a cogeneration system using a fuel cell that can recover the heat energy from the waste heat generated in the power generation system using a fuel cell through a simplified path. There is a purpose.

In addition, another object of the present invention is to provide a cogeneration system and a cogeneration method using a fuel cell that can efficiently use the heat energy generated in the system by using the fluid generated in the power generation system using the fuel cell.

In order to achieve the above object, a cogeneration system using a fuel cell according to an aspect of the present invention is a system using a combination of heat generated from a fuel cell power generation system, and reactants discharged from a reformer and a fuel cell stack. Steam generating means for recovering the waste heat and generating steam using the reactants and waste heat; Power generation means for generating electrical energy using steam generated from the steam generating means; A condenser for recovering steam discharged from the power generation means and expanding at low pressure; And pressurizing means for applying a pressure to the working fluid supplied from the condenser and returning it to the steam generating means.

It may further include a heating means for supplying thermal energy to the steam generating means.

The steam generating means has a plurality of inlets for recovering the fluid or gas flowing from the reformer and the stack, the inlet for recovering the reactant and waste heat discharged from the reformer is relatively higher than the surface of the fluid recovered therein It is preferably formed in the inlet for recovering the reaction material and waste heat discharged from the stack is formed on the lower portion than the surface of the fluid recovered therein.

The power generation means includes energy conversion means for converting the steam generated from the steam generating means into mechanical energy; And a generator for generating electrical energy using the mechanical energy.

Preferably, the condenser may supply a condensed working fluid and a heat exchange medium used for condensation of the working fluid to a heating / hot water supply device.

More preferably, the heat exchange medium used in the condenser may be condensed water.

The cogeneration method according to another aspect of the present invention, in the method using heat generated in the fuel cell power generation system, recovers the reactant and waste heat discharged from the reformer and the fuel cell stack, and uses the reactant and waste heat to steam Steam generation step of generating; A power generation step of generating electrical energy using the steam generated through the steam generation step; A condensation step of recovering and condensing steam discharged from the power generation step; And applying pressure to the working fluid condensed through the condensation step and returning the same to generate steam again.

The steam generation step may be further supplied with thermal energy from an external heat source.

In addition, the steam generation step is provided with a plurality of inlets for recovering the fluid or gas flowing from the reformer and the stack, the reactant and waste heat discharged from the reformer is formed on the upper side of the relatively recovered surface It is preferable to recover through the inlet, and the reactant and the waste heat discharged from the fuel cell stack through the inlet formed at a lower portion than the surface of the fluid recovered therein.

The power generation step includes converting the steam generated from the steam generation step into mechanical energy; And generating electrical energy using the mechanical energy.

It is preferable to supply the heating / hot water supply device with the working fluid condensed in the condensation step and the heat exchange medium used for condensation of the working fluid.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

1 is a configuration diagram of a fuel cell power generation system according to a preferred embodiment of the present invention, Figure 2 is a schematic configuration diagram of a steam generating means according to a preferred embodiment of the present invention. 1 and 2, a fuel cell power generation system according to an embodiment of the present invention includes a reformer 1, a fuel cell stack 3, power transmission means 5, steam generating means 10, and power generation means ( 21, 22, a condenser 30, and a pressurizer 50.

The reformer 1 extracts hydrogen gas from an externally supplied fuel (methanol, ethanol, LPG, or natural gas, etc.) and water through an oxidation catalyst reaction and a reforming catalyst reaction, and generates the hydrogen gas into a fuel cell stack. Supply to (3). At this time, the reformer 1 generates heat at a high temperature due to catalytic reaction with a reforming gas such as trace amounts of carbon dioxide, methane gas, and carbon monoxide.

The carbon monoxide generated in the reformer 1 may enter the fuel cell stack 3 and may adversely affect the catalytic reaction. Therefore, the reformer 1 is preferably equipped with a carbon monoxide remover to remove the carbon monoxide.

In addition, the reformer 1 recovers the reformed gas and supplies the reformed gas to the steam generating means 10 through a gas flow pipe.

On the other hand, the heat generated by the catalytic reaction in the reformer 1 is recovered to the steam generating means 10 through a heat exchange means (not shown), such as a cooling device. The cooling device has a path through which cooling water can be circulated, and the cooling water discharged through the path is supplied to the steam generating means 10 to recover heat due to the catalytic reaction.

The fuel cell stack 3 uses the hydrogen gas supplied from the reformer 1 and air supplied from the outside to generate electricity, heat, and water according to the reaction according to Scheme 1 below.

The anode ^{_{reaction: H 2 -> 2H + +}} 2e -

O₂ + 2H⁺ + 2e^- -> H₂OCathode reaction:

_{^{O 2 + 2H + + 2e -}} -> H 2 O

O₂ -> H₂O + 전류 + 잔열Total reaction: H ₂ +

O _2- > H ₂ O + current + residual heat

Referring to Scheme 1, hydrogen gas is supplied to the anode electrode, and air is supplied to the cathode electrode. The hydrogen gas introduced into the anode electrode is converted into electrons (e ⁻ ) and hydrogen ions (H ⁺ ) in the catalyst layer. In addition, the anode also converts electrons (e ⁻ ) and oxygen ions (O ₂ ) at the cathode due to the catalyst. At this time, when hydrogen ions (H ⁺ ) are moved to the anode electrode through the electrolyte membrane is reacted with oxygen ions (O ₂ ) is converted into water (H ₂ O). Electrons (e ⁻ ) generated at the anode electrode do not move through the electrolyte membrane, but move to the cathode electrode through an external circuit, thereby forming a predetermined current.

At this time, a predetermined heat energy is applied to the water generated by the chemical reaction, and the water is supplied to the steam generating means 10.

The power transmission means 5 is a means for transmitting DC power generated in the fuel cell stack 3 or AC power generated in the power generation means 21 and 22 to the power receiving end.

Preferably, the power transmission means 5 may be transmitted by DC power or AC power in consideration of the power used or power transmission efficiency of the power receiving end. Accordingly, the power transmission means 5 converts the state of the power generated by the fuel cell stack 3 and the power generation means 21 and 22 (DC power-> AC power or AC power-> DC power). It may further include.

The steam generating means 10 includes a first inlet 11, a second inlet 12, a third inlet 13, a fourth inlet 14, and an outlet 15.

The reformed gas discharged from the reformer 1 is returned to the first inlet 11, and the heat exchange medium (eg, cooling water) discharged from the heat exchange means (for example, a cooling device) is returned to the second inlet 12. The working fluid returned from the pressurizing means 50 flows into the third inlet 13. The water supplied from the fuel cell stack 3 flows into the fourth inlet 14.

Preferably, the first inlet 11 and the second inlet 12 are located on the upper side relative to the surface of the fluid in consideration of the amount of fluid (cooling water and water) flowing into the steam generating means 10. The fourth inlet 14 is designed to be located on the lower side relatively than the surface of the fluid in consideration of the amount of fluid (cooling water and water) flowing into the steam generating means 10.

In addition, the outlet 15 is designed to be located on the upper side relative to the surface of the fluid in consideration of the amount of fluid (cooling water and water) flowing in to discharge the steam generated inside the steam generating means 10. do.

Preferably, it may further include a heating means 17 for supplying thermal energy to the liquid contained in the steam generating means (10). When the heat amount of the fluid recovered by the steam generating means 10 is small, the heating means 17 supplies heat energy to the fluid to vaporize the liquid solution.

The power generation means 21 and 22 include a turbine 21 and a generator 22. The turbine 21 has a plurality of rotary vanes positioned on a flow path through which the steam supplied from the steam generating means 10 moves to the discharge port. By the steam continuously supplied from the steam generating means 10 a plurality of the rotary blades are rotated continuously around the rotating shaft, and transmits the rotational force applied to the rotating shaft to the generator.

The generator 22 generates a predetermined electric energy (for example, direct current power or alternating current power) by using the rotational force transmitted from the turbine 21 and transmits it to the power transmission means 5.

The condenser 30 takes the amount of heat equivalent to the latent heat of condensation of the steam discharged from the turbine 21 from the steam to liquefy to generate the working fluid L1.

Preferably, the condenser 30 liquefies the steam using the condensed water (L2). In this process, the thermal energy of the steam is transferred to the condensate (L2) to heat the condensate (L2).

Furthermore, the condensed water L2 receiving the thermal energy of the steam may be supplied to the heating / hot water supply device 40 while being heated to a predetermined temperature and used as heating or hot water for heating.

The pressurizing means 50 applies a predetermined pressure to the working fluid L1 supplied from the condenser 30 to reduce the volume of the working fluid L1 and vaporizes it (the working fluid whose volume is reduced). Return to the generating means (10).

The power transmission means 5 transmits electric energy applied from the fuel cell stack 3 and the generator 22 to a power receiving end, for example, a substation or a power distribution panel.

Hereinafter, the operation of the cogeneration system using a fuel cell according to an embodiment of the present invention with reference to the above-described components. In addition, it describes a cogeneration method according to an embodiment of the present invention.

First, the reformer 1 receives fuel (methanol, ethanol, LPG, or natural gas, etc.) and water from the outside to extract hydrogen gas (H ₂ ) through an oxidation catalyst reaction and a reforming catalyst reaction.

Next, the hydrogen gas H ₂ is supplied to the anode electrode of the fuel cell stack 3, and air is supplied from the outside to the cathode electrode. As described in Chemical Formula 1, the supplied hydrogen gas and air react at the anode electrode and the cathode electrode and are converted into current, water, and residual heat. At this time, the current generated in the fuel cell stack 3 is transmitted to the power transmission means 5, the water containing the residual heat is recovered to the steam generating means (10).

On the other hand, reformed gas such as carbon dioxide, methane gas, and carbon monoxide generated in the process of extracting hydrogen from the reformer 1 is recovered by the steam generating means 10. In addition, in the process of discharging hydrogen, high temperature heat is generated due to the oxidation catalyst reaction and the reforming catalyst reaction, which is a high temperature heat through the heat exchange means (for example, a cooling device using cooling water). The coolant to which the high temperature heat is applied is recovered to the steam generating means (10).

The temperature of the reformed gas and the coolant discharged from the reformer 1 is relatively higher than the temperature of the water generated in the fuel cell stack 3, and the reformed gas and the coolant recovered from the reformer 1 is the fuel cell stack 3. ) Is relatively higher than the water recovered. Therefore, the steam generating means 10 induces a smooth convection effect of the fluid flowing into the inside, and minimizes the heat loss to discharge the steam.

The discharged steam is continuously supplied to the turbine 21, and rotates the rotary blades provided in the turbine 21. As the rotary vanes rotate, the rotational force generated about the rotary shaft is transmitted to the generator 22. The generator generates the predetermined electric energy by using the rotational force and transmits it to the power transmission means (5).

On the other hand, the steam discharged after passing through the turbine 21 is recovered to the condenser 30. The condenser 30 takes the amount of heat equivalent to the latent heat of condensation of the vapor to liquefy and produces a liquefied working fluid L1. At this time, the thermal energy corresponding to the latent heat of the steam is transferred to a heat exchange medium, for example, cooling water (L2). The cooling water L2 having received the thermal energy is moved to the heating / hot water supply device 40 as a fluid having a predetermined temperature and used as heating water or hot water for heating. The condenser 30 supplies the working fluid L1 to the heating / hot water supply device 40 corresponding to the amount of the gas and the fluid flowing into the steam generating means 10, and the heating / hot water supply device 40. ) Uses the working fluid L1 as heating water or hot water.

Next, the remaining fluid L1 supplied from the condenser 30 to the heating / hot water supply device 40 is returned to the steam generating means 10 while being pressurized through the pressurizing means 50.

By using the above-mentioned system to aggregate and use the steam and fluid generated from the reformer 1 and the fuel cell stack 3 into a single steam generating means 10, the fluid path is simplified and the heat loss of the recovered fluid is reduced. It can be minimized.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

According to the cogeneration system and the cogeneration method using the fuel cell of the present invention, there are the following advantages.

First, regardless of the physical properties of the fluid (temperature, condition, flow rate), it can be collected in a single space and used as a preheating source for steam generation.

Second, it is possible to minimize the flow loss in the system by shortening the path of the fluid flowing out of each device.

Third, by using the recovered fluid as it is as a working fluid, it is possible to most efficiently utilize the waste heat and arrangement of the fluid without a special heat exchanger.

Claims (11)

In the system using a combination of thermal energy generated from the fuel cell power generation system, Steam generating means for recovering reactants and waste heat discharged from the reformer and the fuel cell stack, and generating steam using the reactants and waste heat; Power generation means for generating electrical energy using steam generated from the steam generating means; A condenser for recovering steam discharged from the power generation means and expanding at low pressure; And And a pressurizing means for applying a pressure to the working fluid supplied from the condenser and returning it to the steam generating means. The method of claim 1, Cogeneration system using a fuel cell, characterized in that it further comprises a heating means for supplying thermal energy to the steam generating means. The method of claim 1, The steam generating means has a plurality of inlets for recovering the fluid or gas flowing from the reformer and the stack, The inlet for recovering the reactant and the waste heat discharged from the reformer is formed on top of the surface of the fluid recovered therein, and the inlet for recovering the reactant and the waste heat discharged from the stack is the surface of the fluid recovered therein. Cogeneration system using a fuel cell, characterized in that formed in a relatively lower portion. The method of claim 1, wherein the power generation means Energy conversion means for converting steam generated from the steam generating means into mechanical energy; And A cogeneration system using a fuel cell, comprising: a generator for generating electrical energy using the mechanical energy. The method of claim 1, wherein the condenser A cogeneration system using a fuel cell, wherein the condensed working fluid and a heat exchange medium used for condensation of the working fluid are supplied to a heating / hot water supply device. The method according to claim 1 or 5, The cogeneration system using a fuel cell, characterized in that the heat exchange medium used for the condenser is condensed water. In the method using the thermal energy generated in the fuel cell power generation system, A steam generation step of recovering reactants and waste heat discharged from the reformer and the fuel cell stack, and generating steam using the reactants and waste heat; A power generation step of generating electrical energy using the steam generated through the steam generation step; A condensation step of recovering and condensing steam discharged from the power generation step; And And applying pressure to the working fluid condensed through the condensation step and returning the same to generate steam using the same. The method of claim 7, wherein The steam generation step is a cogeneration system, characterized in that further receiving heat energy from an external heat source. The method of claim 7, wherein The steam generation step has a plurality of inlets for recovering the fluid or gas flowing from the reformer and the stack, Reactants and waste heat discharged from the reformer are recovered through an inlet formed at an upper portion relative to the surface of the fluid recovered therein, and reactants and waste heat discharged from the fuel cell stack are relative to the surface of the fluid recovered therein. Cogeneration method characterized in that the recovery through the inlet formed in the lower portion. The method of claim 7, wherein the power generation step Converting the steam generated from the steam generation step into mechanical energy; And Generating electrical energy by using the mechanical energy; cogeneration system comprising a. The method of claim 7, wherein The cogeneration system comprising supplying a working fluid condensed in the condensation step and a heat exchange medium used for condensation of the working fluid to a heating / hot water supply device.

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